1. Field of the Invention
This invention is related to: concrete panels for use in making concrete decks or floors for spanning between structural supports, e.g. pre-cast, pre-stressed concrete panels for constructing reinforced concrete decks for bridges supported by structural beams; parts of such concrete panels, e.g. shear connectors, thread formers, and resilient anchored grout seals; tools for manipulating resilient grout seals; co-acting forms for producing the panels; interior and overhang panels; and apparatus and methods for fabricating and using the panels.
2. Description of the Prior Art
The construction of reinforced concrete decks and floors (e.g. on bridges and in buildings) has always been the most labor intensive and most costly component of the superstructure involved, and has been the component that controls the overall rate of progress of the construction. The need for temporary support of the reinforcing steel and freshly poured concrete until the concrete has attained sufficient strength to support: itself is a major factor in the cost of such construction. The length of time such support must remain in place to allow the concrete to attain sufficient strength is the major factor in controlling the rate of progress of the structure.
The original method used in modern times to provide the temporary support was a basic wood form made up of boards or plywood sheeting nailed to wood joist members, carried on wood timbers or steel beams, which in turn were supported on posts or columns from the ground or lower completed floor. This method is still used today with the development of a variety of complex high capacity column scaffolding systems and beam members that are adjustable for both span length and camber. Other developments in the use of the basic wood form include hanger systems that provide for hanging the form from the beam members of the permanent structure, thereby eliminating the need of posts or columns from below. This development includes hanging brackets to provide for support of deck or floor that cantilevers off of these beams. Another development involved trussed framing systems that provided for the support of large areas of form on a very few bearing supports, and for the removal and re-setting of such large areas as a single unit.
The cost of using basic wood forms would be prohibitive if they were used just once, but they are normally not consumed or destroyed in a single use and are in fact in normal practice re-used many times before wear and tear makes them unfit for further re-use. The greater the number of re-uses of the forms, the more economical they become. Economics therefore dictates that the effort on any given construction project is to provide the minimum quantity of form that will permit reasonable progress to be achieved on the project, thereby gaining the greatest number of re-uses, even though availability of a greater quantity of form would provide for a faster rate of progress.
The setting of wood forms preparatory to the placement of reinforcing steel and concrete is a labor intensive task by itself, but removing wood forms after the concrete has attained sufficient strength, usually requiring extensive scaffolding, requires a greater amount of costly labor and equipment, and the moving to the location of its next use and the clean up and preparation for re-use of the forms adds more labor and equipment cost.
These high labor and equipment costs, and the limitation of progress inherent in the use of wood forms, has encouraged development of alternate methods of providing support for deck and floor construction. The development of methods using materials that are durable, yet economical enough to be used once and then left in place, are gaining in favor. Some methods provide temporary support only and after the concrete has gained its strength and are simply left idle in place. Light gage galvanized corrugated sheet steel panels supported directly by the permanent structure beams is the most popular of these methods.
Some methods provide temporary support but in addition become an integral permanent working part of the structure when the concrete gains its strength. Heavy gage corrugated sheet steel panels, supported directly by the permanent structure beams, with steel loop shear connectors connected (e.g. by welding) to the panels and then embedded in the concrete to make the panels and the cured concrete work as a composite unit is one example of this method. The most recent development in this area is the pre-cast pre-stressed concrete panel supported directly by the permanent structure beams, and again with shear connectors to make the panels and the cast-in-place concrete work as a composite unit. These panels replace the wood forms and serve both as a form and then as an integral part of the structure. A desired amount of concrete is poured onto the already-formed and already-hardened panel.
In becoming a permanent composite component of the structure, the panels replace structural materials that would otherwise have to be provided in the design of the structure. In the case of the sheet steel panels, part of the reinforcing steel is replaced by the panel. In the case of the pre-stressed concrete panel, part of the reinforcing steel and a substantial part of the concrete is replaced by the panel.
In exposed structures such as bridges, the concrete panels are popular with engineers and architects because they blend in with the appearance of the structure and provide the most natural look. Another important reason is that they are not subject to corrosion that might diminish the appearance of the structure at some later date, or even become a hazard by falling from the structure as sheet steel might do.
The currently popular design of pre-stressed concrete panels leaves serious and costly problems in the construction technique. To accomplish the composite relationship between the panel and the cast-in-place concrete, the first requirement is that the panel have a continuous rigid bearing contact with the top of the supporting beam along its ends. Since neither the top of the beam or the bottom of the panel can be depended upon to be perfectly flat, an intervening material, normally concrete or cement grout, that can be installed in a plastic state so it will conform to both surfaces and then harden in that shape is required. General practice (see FIG. 1) is to place a narrow strip of fiberboard along the edges of the top flange of the supporting beam, to set the concrete panel thereon so the panel overhangs the fiberboard strip over the beam, and then to either force the intervening material in its plastic state under the overhanging part of the panel, or to wait until the cast-in-place concrete is poured and at that time to force grout contained in the concrete mix being used to flow under the overhanging part of the panel. The fiberboard is of sufficient thickness to allow room for the intervening material to be forced under the overhanging part of the panel, and it prevents the plastic material from flowing over the edge of the beam. The fact that the two surfaces are substantially parallel and close together requires substantial effort and great care to insure that this important requirement is actually accomplished, and that no air pockets are entrapped that would reduce the bearing area.
To provide for the deflection of the beams and the design cambers that are required to provide the desired finished grading, the designer and/or the constructor is left with three undesirable options in the use of this method. The thickness of the fiberboard material (or other filler or sealing material) can be varied to compensate for deflection and camber which allows the thickness of the slab to remain constant; the thickness of the slab can be varied to provide the desired top surface grading while the bottom surface follows the deflection of the beams; or the top surface of the beams can be re-graded to provide for deflection and camber with a cast-in-place concrete overlay prior to the placement of the fiberboard strips.
If the thickness of the fiberboard strip is varied, (see FIG. 1) measurement and placement of the strips according to a pre-calculated layout must be done by workmen working on top of the bare beams before the panels can be placed. This is slow and dangerous work, and completed work can easily be knocked or blown off of the beam, and at best the amount of variation that can be accomplished is very limited because excessive thicknesses of the fiberboard become unstable. Methods of using concrete bricks under the panels along with galvanized sheet steel (see FIG. 3) to close the opening between the panel and the top of the beam between bricks are available, but are extremely labor intensive and time consuming. There is no way to adjust panels after they are in place, so if errors are discovered at this time the only way to make corrections is to remove the panels and start over.
If the thickness of the slab is varied, all the variation must be in added thickness, since design requirements are minimum thickness. The cost of the excess concrete is a complete loss and again the amount of variation that can be accomplished is very limited because too much excess material would add too much dead load to the slab and the structure.
Re-grading of the top surface of the beam (see FIG. 2) provides satisfactory results, but is clearly the most costly and time consuming of all of the options.
None of the currently used methods have attempted to improve on or replace the use of the basic wood form to support the overhanging portion of decks or floors. Therefore structures that are designed with overhanging deck or floor currently have the progress limitation problem of the basic wood form, even if other non-restrictive methods of support are used between beams.
The facilities for casting pre-stressed concrete panels consists of a pair of anchorages used to anchor the ends of the pre-stressing strands, with a fixed flat surface between them on which the concrete is poured, and usually with fixed side forms the full length of the flat surface to contain and shape the concrete on the sides of the panels. The most expensive part is the anchorages which must be capable of withstanding tremendous horizontal loads as the pre-stressing strands are stretched between them. The anchorages are therefore usually spaced far apart, and the casting beds are very long (e.g. 300-600 feet) and narrow (e.g. 8 feet wide) so as to provide the greatest possible amount of casting capacity for the pair of anchorages.
Once the casting bed is established, the work of casting the typical panels involves the placing and stressing of the strands, the setting of forms which divide the long bed into the lengths of panels required, and the placing of reinforcing steel and the pouring of the concrete. After the concrete has cured, the strands are released from the anchorages and cut at each form, and the panels are removed from the bed. The setting and removing of the forms is clearly the most difficult of these tasks. The form must have two faces against which the concrete is poured and through which all the strands must pass. The strands are usually spaced on approximately six inch centers across the full width of the bed at mid-depth of the panels. The two faces of the form are spaced apart to provide for the strands to be exposed between panels so that after they are cut, a required length will extend out of the end of each panel to provide anchorage into the cast-in-place concrete when the panel is installed in the bridge or building. Since the strands effectively divide the faces into two halves, the two faces are usually split longitudinally so the lower half can be set below the strands, before the strands are installed, while the upper half is set above the strands, after they are installed. Holes must be provided along the joint between the top and bottom halves of the form with a close enough fit to the strands to prevent excessive grout leakage, and the top and bottom halves must be fixed in alignment at the joint. The forms must be maintained in their selected positions to resist the forces of the concrete being poured against them and the space between the two faces must be covered to prevent it from being filled with concrete. In current practice the typical divider form is made up of a bottom board or a steel channel with wood filler of a width equal to the required space between concrete faces, a thickness equal to the space under the strands, and a length equal to the width of the casting bed. Wood boards the width of the bottom member of a thickness equal to the diameter of the strands, and a length equal to the space between strands, are nailed to the top form, to fill the space between strands and provide a notch for each strand at the proper locations. The top board of the same dimensions as the bottom form is nailed or bolted in place over the strands after they have been placed and stressed.
The pre-cast pre-stressed concrete panels that are in use for deck and floor construction today eliminate some of the need for labor intensive temporary wood support forms to be furnished, set in place, and later removed and prepared for re-cycling. The "set in place one time and never go back" use and therefore the elimination of the need to re-cycle the support means as with temporary wood forms permits the constructor to economically work a much larger area of deck or floor at one time, the only limitation being the re-cycling of the support forms for the overhanging part of the slab. Labor crews and equipment can be utilized more efficiently and progress of the deck or floor is substantially improved. But for all their advantages, there remain distinct problems in the way they are used today. Pregrading and erecting them in place, especially the pregrading, is highly labor intensive; forcing grout or concrete under the ends of the panels is difficult; and on structures with substantial overhanging slab area, such as bridges, the overhanging area is dealt with using the basic re-cycling wood form. There has been a long-felt need for efficient and economical apparatuses and methods for casting concrete panels and for making a concrete deck to span structural supports. There has also been a long-felt need for such a deck that is quick to set and easy to grade. The present invention meets and satisfies these needs.
In accordance with 37 C.F.R. .sctn..sctn.1.56 and 1.97, the following references are disclosed:
1. Dayton Superior Bridge Deck Forming Handbook, 1985, which discloses various prior art hangers, decks, overhang brackets, guardrails, precast girders, screed supports, and reinforcing bars. PA1 2. Dayton Superior Precast--Prestressed Concrete Handbook 1986 which discloses various prior art inserts, anchors, braces, and bolts. PA1 3. CMI News, Spring 1982, discloses prior art deck methods. PA1 4. Superior Bridge Deck Forming Handbook, 1977, discloses various prior art hangers, brackets and various methods for making decks. PA1 5. Texas Highway Department Bridge Division, Prestressed Concrete Panels Optional Deck Details, 1980, Sheets 129 Band C, discloses prior art panels and methods for making decks. PA1 6. U.S. Pat. No. 122,498 discloses a method for making concrete pavement. PA1 7. U.S. Pat. No. 1,004,410 discloses apparatus for laying concrete. PA1 8. U.S. Pat. No. 1,751,147 discloses a method of lining tunnels with concrete. PA1 10. U. S. Pat. No. 3,646,748 discloses a tendon for prestressed concrete. PA1 11. Russian Patent No. 502,076 discloses bridge surface concreting machines.
None of these references taken alone or in any combination teaches or suggests the present invention.